Kristien L. Verheyen

Background Up‐to‐date estimates of early‐life morbidity and mortality in Thoroughbreds are lacking. Methods A birth cohort was established on Thoroughbred stud farms across the UK and Ireland. All veterinary interventions for disease or injury between birth and 18 months of age or leaving the study were recorded. Multilevel Poisson regression models with farm and foal as random effects were fitted to estimate incidence rates. Results Data were available for 3328 foal‐months at risk for 275 foals on seven farms. The overall rates of disease and injury requiring veterinary intervention and mortality were 11.9 cases/100 foal‐months at risk (95% confidence interval [CI] 8.6–16.2) and 0.2 cases/100 foal‐months at risk (95% CI 0.1–0.4), respectively. Almost half ( n = 133/273, 49%, 95% CI 43–55) of the live‐born cohort required veterinary intervention for musculoskeletal disease or injury, equating to 5.8 cases/100 foal‐months at risk (95% CI 4.1–8.2), predominantly reported as developmental orthopaedic disease (DOD). Limitations Convenience sampling of participants may affect the generalisability of the findings. Conclusions Rates of musculoskeletal disease and injury, in particular DOD, on Thoroughbred stud farms were high. Further work to identify modifiable risk factors and further understanding of the economic impact of these conditions and long‐term consequences for musculoskeletal health and performance is required.